Question: How many cubic millimeters fit in $9$ cubic centimeters?
First we will figure out how many cubic millimeters fit in one cubic centimeter. There are $10$ millimeters in every centimeter. So a cubic centimeter is the same as a $ 10 \text{ mm} \times 10 \text{ mm} \times10 \text{ mm} $ cube. $1 \text{cm} = 10 \text{mm}$ There are $10 \times 10 \times 10 = 1000 \text{ mm}^3 $ in each cubic centimeter, by the volume formula. Since we have $9$ cubic centimeters, and each cubic centimeter holds $1000$ cubic millimeters, we have a total of $9 \times 1000$ cubic millimeters. So $9000$ cubic millimeters fit in $9$ cubic centimeters.